1. Field of the Invention
The present invention relates to a planar antenna, in particular to an embedded multiband/wideband planar antenna having a slender area with a limited width.
2. Description of the Related Art
In an antenna design, a metal sheet is generally used for making a reflector or a ground plane of the antenna. After the metal sheet is disposed and a sufficient distance is kept between the metal sheet and the antenna, the antenna not only increases the antenna gain effectively, but also decreases the backward radiation of the antenna to reduce unnecessary energy losses. However, present communication products tend to become increasingly smaller, and the height of antennas depends on an overall height of a product, and thus a compact and low profile design is required. For example, the antenna of a notebook computer is generally designed and disposed at the top or both sides of a computer screen. As shown in FIG. 1, an available space is a slender area with a limited width, and thus the antenna may be designed on a printed circuit board at a back panel of the computer screen. However, if the metal ground plane and the antenna are very close to one another as shown in FIG. 2, an inverted L-shaped monopole antenna will be used. Since the distance between a horizontal arm of the antenna and the ground plane is too close, an image current produced on the ground plane 2 is in the opposite direction to the current on the antenna and thus will be offset by each other and result in poor antenna gain and radiation efficiency.